Abstract: Device ensuring filtration and communication between the atmosphere and a crankcase with oil sump, of the type comprising a housing provided with vents and containing a filter cartridge which defines a volume which communicates, on the one hand, with the outside through a filtering agent, and on the other hand, with the housing, through a vertical passage. The device further comprises internal means for recovering and recycling the oil from the filter medium as well as internal means for placing the housing in direct communication with the atmosphere in case of clogging-up of the filtering agent.